How much will 1 L of glacial acetic acid weigh? 1000 mL x 1.05 g/mL = 1050 grams.
How much of that is acetic acid. If it's glacial acetic acid, it is 100% acetic acid so all 1050 g is HC2H3O2.
How many moles is that?
1050 grams/molar mass = 1050/60 = 17.50 M.

The new concn will be 17.5 M x (20 mL/1300 mL) = ?? M (or you can do a mL x M = mL x M and come up with the same thing).